The design of safety relief valves depends on knowledge of the expected force-lift and flow-lift characteristics at the desired operating conditions of the valve. During valve opening the flow conditions change from seal-leakage type flows to combinations of sub-sonic and supersonic flows It is these highly compressible flow conditions that control the force and flow lift characteristics. This paper reports the use of computational fluid dynamics techniques to investigate the valve characteristics for a conventional spring operated 1/4” safety relief valve designed for gases operating between 10 and 30 bar. The force and flow magnitudes are highly dependent on the lift and geometry of the valve and these characteristics are explained with the aid of the detailed information available from the CFD analysis. Experimental determination of the force and flow lift conditions has also been carried out and a comparison indicates good correspondence between the predictions and the experiment. However, attention requires to be paid to specific aspects of the geometry modeling including corner radii and edge chamfers to ensure satisfactory prediction.

The side force produced by the injection of secondary gas into the supersonic regime of a main nozzle is investigated with particular reference to the effect of the angle between the secondary jet and the main nozzle axis. In the experiments, downstream and upstream injection angles at one secondary port location in the main nozzle were examined. It is shown that there is a definite advantage to be gained by injecting the secondary gas in an upstream direction. An analytical analysis of the results indicates that for moderate secondary mass flows maximum side force is produced when the angle between the axis of the secondary port and the normal to the axis of the main nozzle is in the range 40-50°. When injecting a given secondary mass flow at the angle for maximum side force the axial thrust augmentation is almost zero. As the angle of injection is reduced from upstream values to downstream values the side force reduces and the thrust augmentation increases, indicating that thrust augmentation can be used to determine how effectively a given mass flow of secondary fluid is being utilized in the production of side force.

Directional control of rockets can be achieved by using secondary gas jets for providing side forces. The present investigation is concerned with the fact that a greater side force can be achieved by expanding the secondary gas into the supersonic region of the main nozzle than by expanding it directly to atmosphere. A laboratory test rig using ambient temperature air for the primary and secondary flows is described. Axial thrust and side force were measured using strain gauge force transducers. The experiments were performed on a small axisymmetric main nozzle with a 10° semi-angle of divergence and with sonic injection through circular ports placed normal to the main nozzle axis. The investigations centred principally on the effects of (1) varying the secondary port size at a given axial location in the nozzle and of (2) varying the axial location of a port of constant diameter. Side force and axial thrust augmentation characteristics were obtained for a range of primary and secondary flow inlet pressures. The results show the relative importance of the parameters on which side force depends, the maximum side force that may be produced and the interdependence of axial thrust augmentation and side force.

This presentation describes both the experimental measurement and finite element analysis used to study the temperature distribution during a metal inert gas (MIG) welding process, including the cooling down period. Welding was carried out on two pieces of 6 mm thick mild steel plates of size 200 mm by 75 mm with a 2 mm square gap between them. Simulation of the whole process was done using ANSYS 5.7 finite element software. The object of the exercise was to develop analytical techniques to accurately predict the temperature history of the weldment, which could be further used to analyse problems such as distortion of the weldment, residual stress formation and cracking phenomena. The experimental and computational results were found to be in very good agreement

This work is concerned with the optimization of the method by which secondary gas is used to produce side force in rocket nozzles and is part of a series of investigations in which the effects of secondary port area, port location in the main nozzle and the angle between the axes of the main and secondary nozzles have been studied. In this note the merits of using multiport configurations for introducing the secondary gas as compared with using a single port of equivalent area are considered. It is shown that, at a given location for introducing the secondary flow, multiport arrangements of either the radial or parallel type give side forces less than that produced by a single port passing the same secondary mass flow.